Effect of a high maternal dietary intake during mid-gestation on components of the utero-placental insulin-like growth factor (IGF) system in adolescent sheep with retarded placental development

The aim of the present study was to investigate the effects of administerin g a high plane diet during early to mid-gestation on the uterine and placen tal insulin-like growth factor (IGF) system and on systemic IGF-I concentra tions in pregnant adolescent ewes with restricted placental growth. Embryos recovered from superovulated ewes inseminated by a single sire were transf erred in singleton to the uterus of adolescent recipients. After transfer e wes were offered a high (H) or moderate (M) amount of a complete diet calcu lated to promote rapid or normal maternal growth rates, respectively. Five ewes from each group were switched from either M to I-I or H to M diets at day 52 of gestation. Maternal and fetal blood samples and placental tissues were collected from all animals at day 104. Ewes on the high plane diet fr om mid-gestation (HH, MH groups) had restricted placental mass (P < 0.01) a nd tended to have smaller fetuses. This was associated. with increased mate rnal plasma IGF-I concentrations (P < 0.001). The pattern of expression of components of the IGF system in the uterus and placenta was studied by in s itu hybridization. IGF-I mRNA concentrations were below the limit of detect ion. IGF-II mRNA expression was high in the fetal mesoderm and present in m aternal stroma, but was not influenced by nutritional treatment. In contras t, IGF binding protein 1 (IGFBP-1) mRNA expression was higher (P < 0.05) an d IGFBP-3 mRNA expression was lower (P < 0.05) in the endometrial glands of ewes in HH and MH groups. In the fetal trophoblast, IGFBP-3 mRNA expressio n was higher in the MH group. Type 1 IGF receptor expression was increased (P < 0.01) in the luminal epithelium of the HM group and IGFBP-2 mRNA expre ssion was highest in the placentome capsule of ewes in the HH group. Togeth er, these results indicate that reprogramming of the uterine and placental IGF axis by maternal nutrition could contribute to placental growth retarda tion in growing adolescent sheep.